This invention relates to a front loaded cylinder for a door lockset and particularly relates to a door lockset having a cylinder lock which can be removed from or inserted into the front of the lockset without dismantling the lockset from its assembly with a related door.
Some door locksets include a cylinder lock which is typically located in the door operator, such as a knob, or within a guard collar of a deadlock. Such a cylinder lock includes a cylinder body which is formed with a cylindrical opening for receipt of a cylindrically shaped plug for rotation therein. The cylinder body and plug are each formed with a plurality of aligned holes which receive and support sets of spring-biased tumbler pins. Normally, various pins overlap a juncture line between adjacent facing surfaces of the cylinder body and the plug to prevent the plug from rotating relative to the cylinder body. This juncture line is referred to as "the shear line."
The plug is formed with a key slot which communicates with the holes of the plug so that portions of the pins extend into the key slot. When an appropriate key is inserted into the slot, bits on the key adjust the position of the pins so that the shear line is clear and the plug can be rotated within the opening of the cylindrical body.
In some locksets, the cylinder lock is assembled from the rear of the lock set. If a need arises to extract the cylinder lock, the lockset must be dismantled from the door and then disassembled to the extent that the cylinder lock can be removed from the rear of the operator. If it is desired to install a replacement cylinder lock, the same time consuming and tedious process is required.
Other types of locksets use cylinder locks which can be inserted from the front of the operator or deadlock guard collar. Such locksets have alleviated some of the difficulties encountered with the rear loaded cylinder locks. Locksets of this type are useful, for example, where it is necessary or desirable to change the lock combination on a frequent basis. For example, where tenants move and keep the key to the existing lockset, the landlord can simply replace the cylinder lock with one of a different combination by the front loading technique.
While the front-loading technique has simplified the process of replacing a cylinder lock, the available front loaded cylinder locks present complex internal mechanisms, the assembly of which is tedious and time consuming. As a consequence, the cost of such locks is relatively high. Any effort to reduce the cost has been at the expense of the level of security provided by such cylinder lock.
Thus, there is a need for a front loaded cylinder lock which maintains a high level of security for the lockset and which is available at a reasonable cost.